The present invention relates to a video entertainment system for passenger vehicles and, more particularly, to a low-height, low-cost, high-gain, leaky wave antenna system disposed in a low-drag radome and a system for providing satellite broadcasted video directly to passengers on mobile platforms such as, for example, airplanes, boats and automobiles.
Various embodiments of antennas for reception of satellite broadcasted signals designed for mounting on vehicles have been studied and proposed. Since such an antenna is to be mounted, for example, on a roof or the like of an automotive vehicle running on a road where the height of the cars are legally restricted or, for example, on an aircraft where height is also an issue with respect to, for example, any drag associated with such an antenna that may result in decreased fuel efficiency, an important feature of such an antenna is to minimize a height of the antenna and an antenna mounting area. In addition, where the antenna is to receive at all possible times the satellite broadcasted signal and thus where the antenna at all times must be pointed in a direction of the satellite which will vary with time as the vehicle moves, it is important to have a tracking mechanism for controlling an azimuth and elevation angle of the antenna. However, the tracking mechanism can constitute a considerable part of the whole antenna manufacturing costs, complexity and height or mounting area of the antenna. Thus, it is important to minimize the space, complexity and requirements of the tracking mechanism and the antenna.
Disclosed, for example, in U.S. Pat. No. 5,579,019 (hereinafter the xe2x80x9c""019 patentxe2x80x9d) is a slotted leaky waveguide array antenna for reception of satellite broadcast electromagnetic waves that may be mounted on a roof of an automobile. In particular, the ""019 patent discloses a slotted leaky waveguide array antenna that enables reception of a direct broadcast satellite signal even with movement of the automobile, by providing an elevation beam width of about xc2x1/xe2x88x925xc2x0 in the elevation direction which is disclosed to be wide enough so that no tracking system need be used to move the antenna in the elevation direction. Thus the tracking mechanism and antenna of the ""019 patent has an economy of scale in that the antenna need only be rotated throughout 360xc2x0 of the azimuth angle. The antenna of the ""019 patent includes a plurality of waveguides disposed in parallel, wherein each waveguide has a plurality of slots disposed along the waveguide axis and having varying offset, length, and intersection angle values determined by a methodology. In addition, the reference discloses that the waveguide antenna array includes a feed waveguide for distributing electromagnetic waves to each of the plurality of waveguides which is disposed in a same plane as the array antenna and includes a first section extending along an end of each of the plurality of waveguides and a second section extending from a center of the antenna to a center of the first section which is perpendicular to the first section to thereby form a T-junction feed waveguide. The feed waveguide allows the antenna to be rotated in the horizontal or azimuth plane at a rotary center of the antenna without subjecting a converter that is coupled to an output of the antenna to any rotation. An asserted advantage of the ""019 patent is that the converter can be kept in a stationary position thereby reducing the stress on the converter and prolonging the life of the converter.
Another issue with the various slotted waveguide antennas that have been proposed are the costs, the ease of manufacture, and the weight of the various waveguide antennas. For example, a conventional slotted waveguide antenna may be manufactured combining metal plates with a proper precision suitable for a desired frequency range to form a plurality of waveguides, and then securing the waveguides to each other in a transverse direction in an array-like manner. Subsequently, or in conjunction, depending upon the position of a feed waveguide, the feed waveguide may then be secured to the waveguide array. However, such a manufacturing process may not be suitable for mass production and therefore such a slotted waveguide antenna array may not be provided inexpensively using such a method. Moreover, such an embodiment of the slotted waveguide antenna may require reinforcement to avoid movement of the waveguides within the waveguide array. Further, such an embodiment of a waveguide may be typically made out of a metallic material with a high specific gravity which is, for example, for aluminum approximately 2.7 and yields a heavy slotted waveguide antenna array. Thus, conventional slotted waveguide antenna arrays are typically bulky, heavy and not suitable for efficient and cost effective mass production.
U.S. Pat. No. 4,916,458 discloses an embodiment of a slotted waveguide antenna that is intended to be manufactured easily, inexpensively and that includes a plurality of radiating waveguides each having at least one radiating slot. The antenna also includes a feed waveguide disposed at one end of each of the plurality of waveguides for feeding the plurality of radiating waveguides and a plurality of apertures between the feed waveguide and the radiating waveguides. The plurality of waveguides and the feed waveguide are formed in a single plane by a dielectric plate that is sandwiched between conductive layers to form broad walls of the plurality of waveguides and the feed waveguide. In addition, either plated through-holes having a gap between each of the plated through-holes that is smaller than a wavelength of a signal propagating in the waveguides, or conductive pins having a similar gap therebetween and that are metalized on both sides, are inserted between the conductive layers and used to form the walls of the plurality of waveguides and the walls of the feed waveguide. In addition, the ""458 patent discloses that outer peripheral walls of the plurality of waveguides and the feed waveguide can be provided by covering the dielectric plate material with a conductive material to form the outer peripheral walls. The slotted waveguide antenna of the ""458 patent is asserted to be easy and inexpensive to manufacture and produce.
It is an object of the present invention to provide an improved leaky waveguide array antenna.
According to one embodiment of the present invention, a leaky waveguide antenna array that receives and/or transmits electromagnetic signals, includes a plurality of radiation waveguides disposed in parallel to each other to form the antenna array. A feed waveguide provides an electromagnetic signal to the plurality of radiation waveguides and/or receives a plurality of electromagnetic signals from the plurality of radiation waveguides and provides a composite electromagnetic signal at an output of the feed waveguide. Each of the plurality of radiation waveguides has a waveguide axis and includes a plurality of apertures arranged in a direction of the waveguide axis. The feed waveguide includes a first section of waveguide having a first end connected to an input/output port. The first section of waveguide has a height substantially the same as the height of each of the plurality of radiation waveguides and the first section of waveguide has a second end coupled to a first junction point. The first junction point transitions from the first section of waveguide to a second section of waveguide and a third section of waveguide that each have a height that is substantially half of the height of the first section of waveguide. The second section of waveguide transitions with an upward ramp to the substantially half height of the first section of waveguide. The third section of waveguide transitions with a downward sloping ramp to the substantially half height of the first section of waveguide. The third section of waveguide is substantially a mirror image of the second section of waveguide. The feed waveguide also includes a septum connected to vertical walls of the first, second and third sections of waveguide which aids in the transition from the height of the first section of the waveguide to the height of the second section and the third section of waveguide. Each of the second section of waveguide and the third section of waveguide are coupled to a corresponding first signal port and second signal port of the feed waveguide. Each of the first signal port and the second signal port are coupled to a corresponding one of the plurality of radiation waveguides.
With this arrangement, an antenna of reduced height and length can be constructed and mounted on a moving platform such as, for example, an automobile and that is part of a system to transmit and/or receive any of live video programming, images, interactive services, two-way communications and other data signals. In addition, the leaky waveguide antenna array and feed waveguide can be construed or molded from a composite material. With this arrangement, the antenna and feed waveguide can be manufactured more easily, reduced in weight as compared to, for example, an antenna assembled out of a metal such as aluminum, and can be provided at a lower cost.
According to another embodiment of the present invention, the leaky waveguide antenna and the feed waveguide can be mounted on an antenna positioning apparatus and disposed within a low-drag radome on a moving vehicle. With this arrangement, the antenna can be moved in both azimuth and elevation angles to keep the antenna pointed at, for example, a transmitting satellite providing broadcast video signal as the vehicle is moving. This embodiment can also be provided with at least one pair of steering arrays also mounted on the antenna positioning apparatus and disposed within the low-drag radome.
Another embodiment of the present invention is a method of providing a signal to passengers within a vehicle, wherein the vehicle is in an area where reception of the signal is not available. The method includes receiving the signal, with a first receiver in an area where the signal is available, and retransmitting the signal, received by the first receiver, to a second receiver that is located on a vehicle that is not within the area where the signal is available. The method further includes the steps of retransmitting the signal received by the second receiver to a third receiver located on a vehicle that is within the area where the signal is not available. The method further comprising the step of repeating the step of retransmitting the received signal to any vehicle which is in the area where the coverage is not available so that each of the vehicles can receive the signal and present it to passengers within each of the vehicles.
With this arrangement, any of live video programming, images, interactive services such as the internet, two-way communications such as telephone communication and other data signals can be provided to passengers within vehicles even though the vehicles are not within an area where the signal can be received due to, for example, a lack of satellite coverage, or non-continuous satellite coverage, or a lack of ground to air communications facilities, or a poor signal quality. This is particularly advantageous for aircraft flight paths such as, for example, transoceanic flights where a plurality of airplanes are lined up in a path traversing an ocean and where satellite coverage is not yet available above the ocean.